Speaking at ThinkPanmure's ThinkTomorrow venture capital summit, Andreessen responded to a question about whether Google's dominant position in search could be challenged. While he said he's a big fan of Google (GOOG), he said plenty of opportunities exist for competitors.

"If you put your hand over the logos of the other top search competitors, they all look like Google," Andreessen said.

Of course, part of Google's early appeal was the simplicity of its sparse search screen, which others have mimicked. "I actually think Yahoo and MSN has helped feed Google's growth by looking more and more like them," he said.

Social networks were the main focus of Andreessen's onstage interview with famed Silicon Valley venture capitalist Ron Conway.

Andreessen co-founded Ning, a platform for letting anyone create a social network. Ning users have created more than 250,000 social networks, and Andreessen predicted it will eventually spawn millions.

The 150-plus effect

While the number of new Ning-powered networks has grown (from personal ones focused on families to special interests and community groups) the number of participants in each one depends on the initial growth rate. Andreessen said 150 users turns out to be a kind of magic figure.

"When there are three to 150, the membership numbers stay pretty stable," Andreessen said. "Virtually all the groups with 150 or over are growing rapidly."

One example is rapper 50 Cent, whose Ning network has hundreds of thousands of members. "He's using it to recruit young ladies for his concerts. He considers it a killer app," Andreessen cracked.

As for social networking in general, Andreessen was very bullish. He noted MySpace has become "the poster child" for the challenge of making money in social networks, "but look closely at the numbers and you see MySpace has generated close to a billion dollars in revenue."

While profits may be slim to none, he added, MySpace and others will likely "make it up in volume" over the long haul.

Andreessen commented that as other media -- including television, newspapers and radio -- continue to bleed red ink, consumers are clearly migrating to the Internet and video games for news and entertainment. "The money has to follow," he said.

He also positioned social networks as part of a much broader trend of killer applications that have emerged over the past decade or so that will help people better connect. As examples, he named eBay (NASDAQ: EBAY), PayPal, Amazon (NASDAQ: AMZN) and Skype, which all have a social component. "People love people -- socialization runs deep in the human DNA," he said.

But he also warned companies that think they can simply add social networking features to more static applications are likely to be disappointed with the results. "I don't think in the long run that's what users want," he said.